Problem: 9 glue sticks cost $17.82. Which equation would help determine the cost of 4 glue sticks?
There are several equations that could help determine the cost, each with a slightly different approach. We can write the fact that 9 glue sticks cost $17.82 as a proportion: $\dfrac{9}{\$17.82}$ Let $x$ represent the unknown cost of 4 glue sticks. Since 4 glue sticks cost $x$ , we have the following proportion: $\dfrac{4}{x}$ The cost changes along with the number of glue sticks purchased, and so the two proportions are equivalent. $\dfrac{9}{\$17.82} = \dfrac{4}{x}$